Field of the Invention
The present invention relates to a user equipment (UE), a base station (BS) and data transmission methods thereof; in particular, the present invention relates to a user equipment, a base station and data transmission methods thereof that adopt the Full Duplex Radio (FDR) mechanism.
Descriptions of the Related Art
Many wireless communication standards (e.g., the Long Term Evolution (LTE) standard) currently available in the market support communication and data transmission of mobile devices in a moving status. According to these wireless communication standards, when a mobile device experiences an attenuated signal strength as it gradually moves away from the serving base station, the mobile device is handed over to another base station that can serve the mobile device (called a “target base station” hereinbelow) to maintain the quality of communication and data transmission thereof. Conventional handover technologies may be classified into hard handover technologies and soft handover technologies. The operation modes and shortcomings of these two kinds of handover technologies will be described briefly.
According to hard handover technology, a mobile device firstly detaches from the serving base station and then connects to a target base station of service. Specifically, if the serving base station determines that the mobile device can be handed over to the target base station, the serving base station transmits data for the mobile device in the buffer thereof to the target base station via a backhaul network. Because the data in the buffer of the serving base station is forwarded via the backhaul network, there is a long latency. The target base station that receives the data forwarded by the serving base station via the backhaul network will allocate a wireless resource in advance for use by the mobile device in subsequent connection. However, in the case that the mobile device fails to connect with the target base station subsequently, the wireless resource allocated in advance cannot be used by other mobile devices and this leads to a waste in wireless resource. If the mobile device is successfully handed over to the target base station, the mobile device detaches from the serving base station. The serving base station will not release information of the mobile device until a notice transmitted by the target base station via the backhaul network is received. However, most of the time, the target base station will not notify the serving base station to release the information of the mobile device until the target base station has transmitted all data forwarded by the serving base station to the mobile device and has decoded an end mark; this also leads to a waste in resources.
According to soft handover technology, a mobile device firstly establishes a control connection with a target base station, then interrupts a data connection with the serving base station, and finally hands over the mobile device to the target base station. Specifically, if the serving base station determines that the mobile device can handover to the target base station, the serving base station also transmits data in its buffer that is to be transmitted to the mobile device to the target base station via a backhaul network. Since the data in the buffer of the serving base station is forwarded via the backhaul network, there is a long latency. According to the soft handover technology, the mobile device will not detach from the serving base station until it has established the control connection with the target base station, so the waste caused by allocating wireless resource in advance of the hard handover technology is avoided. Similarly, if the mobile device successfully handovers to the target base station, the serving base station will not release information of the mobile device until a notice transmitted by the target base station via the backhaul network is received. However, usually the target base station will not notify the serving base station to release the information of the mobile device until the target base station has transmitted all data forwarded by the serving base station to the mobile device and has decoded an end mark; this leads to a waste in resources.
Accordingly, an urgent need exists in the art to provide a data transmission technology that is used in a handover procedure and that overcomes the aforesaid shortcomings.